Question 1

Which of the following best describes a covalent bond according to valence bond theory?

Accepted Answer

A pair of shared electrons represented as a line between atoms.

Question 2

What is the bond angle in methane ($$CH_4) as $$predicted by $$sp^3$$ hybridization?

Accepted Answer

$$109.5^\circ$$

Question 3

Which of the following molecules contains a carbon atom with $$sp^3$$ hybridization?

Accepted Answer

Methane ($$CH_4)$$

Question 4

How much energy is released when one mole of $$H_2$$ molecules forms from two moles of hydrogen atoms?

Accepted Answer

$$436 \ 	ext{kJ/mol}$$

Question 5

Which statement about sigma ($$\sigma) $$bonds is correct?

Accepted Answer

They are formed by the head-on overlap of atomic orbitals along the internuclear axis.

Question 6

In the electron-dot structure of ammonia ($$NH_3$$), how many lone pairs are present on the nitrogen atom?

Accepted Answer

1

Question 7

Which of the following best explains why the $$H_2$$ molecule is more stable than two separate hydrogen atoms?

Accepted Answer

The $$H_2$$ molecule has lower energy due to the formation of a covalent bond.

Question 8

What is the minimum energy point on a plot of energy versus internuclear distance for two hydrogen atoms called?

Accepted Answer

Bond length

Question 9

Which hybrid orbitals are involved in the carbon–carbon bond of ethane ($$C_2H_6$$)?

Accepted Answer

$$sp^3$$ hybrid orbitals

Question 10

A student draws the electron-dot structure for water ($$H_2O) $$and shows only two bonds and no lone pairs. What is the error in this structure?

Accepted Answer

There should be two bonds and two lone pairs.

Question 11

Which of the following statements about $$sp^3$$ hybrid orbitals is true?

Accepted Answer

They have two lobes and are unsymmetrical about the nucleus.

Question 12

If the bond length of the H–H bond in $$H_2 is$$ $$74 \ 	ext{pm}$$, what does this value represent?

Accepted Answer

The distance at which the energy is minimum.

Question 13

Which molecule below is correctly matched with the number of covalent bonds formed by its central atom?

Accepted Answer

Ammonia ($$NH_3$$): three bonds

Question 14

Which of the following best describes the directionality of $$sp^3$$ hybrid orbitals in methane?

Accepted Answer

They are oriented toward the corners of a regular tetrahedron.

Question 15

A chemist wants to break the H–H bond in $$H_2. $$How much energy must be absorbed per mole?

Accepted Answer

$$436 \ 	ext{kJ/mol}$$

Question 16

Which of the following is a correct statement about lone-pair electrons in ammonia ($$NH_3$$)?

Accepted Answer

They are nonbonding electrons located on the nitrogen atom.

Question 17

Which of the following best explains why $$sp^3$$ hybridization leads to stronger bonds in methane?

Accepted Answer

The $$sp^3$$ orbitals are unsymmetrical and have directionality, allowing for strong overlap.

Question 18

In the context of real-world applications, why is the bond energy of $$H_2$$ important in industrial hydrogen production?

Accepted Answer

It indicates the amount of energy required to break $$H_2$$ into atomic hydrogen for chemical synthesis.

Question 19

Which of the following is a correct representation of the electron-dot structure for chloromethane ($$CH_3Cl$$)?

Accepted Answer

A carbon atom with three hydrogens and one chlorine, with lone pairs on chlorine.

Chapter 1: Structure and Bonding – Foundations of Organic Chemistry

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